VLC certainly has issues on my media PC (ASRock ION 330 Pro) where pixellation and heavy stuttering occurs on 720p and up and MPC-HC stutters when playing 1080p using DXVA slightly even though the CPU is a dual core Atom @ 1.66GHz and MPC detects DXVA HW Accel in the ION chipset!
STRANGELY though WMP plays 1080p videos absolutely fine once I install Haali splitter so that DTS/AC3 streams and h264 video could be split and played correctly.
Also FlashHD works flawlessly too using Flash 10.1 so ION is working nicely here
MPC-HC on everything else though.